Solid-state image pickup device and method for manufacturing same, and image pickup apparatus

ABSTRACT

Disclosed herein is a solid-state image pickup device of a type wherein a pixel is configured to include a sensor unit capable of photoelectric conversion, the image pickup device including: a semiconductor substrate; a charge storage region of a first conduction type, which is formed in the semiconductor substrate and constitutes a sensor unit; a charge storage sub-region made of an impurity region of the first conduction type, which is formed, in plural layers, in the semiconductor substrate below the charge storage region serving as a main charge storage region and wherein at least one or more of the plural layers are formed entirely across a pixel; and a device isolation region that is formed in the semiconductor substrate, isolates pixels from one another, and is made of an impurity region of a second conduction type.

BACKGROUND

This disclosure relates to a solid-state image pickup device and amethod for manufacturing same, and also to an image pickup apparatusprovided with the solid-state image pickup device.

In solid-state image pickup devices, in order to make up for reductionin charge storage capacitance ascribed to the miniaturization of pixelsbeing advanced, it has been proposed to additionally form, aside from acharge storage region of an existing sensor unit, an impurity region ofthe same conduction type as the charge storage region therebelow.

Further, there has been proposed a charge storage unit wherein ionshaving different energies are injected plural times into below a chargestorage region to form a plurality of impurity regions, followed bycombination with a known charge storage region (see, for example,Japanese Patent Laid-open No. 2002-164529).

In this Patent Application, a CCD (charge-coupled device) solid-stateimage pickup device is described. With respect to a CMOS (complementarymetal-oxide semiconductor) solid-state image pickup device, a pluralityof impurity regions may be likewise formed beneath a storage imagepickup region of a sensor unit thereby configuring a charge storageunit.

A schematic configuration view (sectional view) of the CMOS solid-stateimage pickup device configured in this way is shown in FIGS. 5A and 5B.FIG. 5A is a sectional view at a face orthogonal to a transfer gate and5B is a sectional view, taken along line X-X′ of FIG. 5A.

It will be noted that although a first charge storage unit and a secondcharge storage unit are mentioned in the Laid-open Patent ApplicationNo. 2002-164529, the hitherto known charge storage region is calledherein main charge storage region and the lower impurity region iscalled charge storage sub-region.

The solid-state image pickup device shown in FIGS. 5A and 5B isconfigured such that individual pixels are isolated with a P⁺ deviceisolation region 53, and a photodiode (PD) of a sensor unit and a chargetransfer portion are formed at the inside isolated with the deviceisolation region 53. In the figures, indicated by 51 is a semiconductorsubstrate (i.e. a semiconductor substrate or a semiconductor substrateand a semiconductor epitaxial layer formed thereon) and by 52 is ap⁻semiconductor well region formed as buried in the semiconductorsubstrate 51. An overflow barrier is formed by the semiconductor wellregion 52.

In this solid-state image pickup device, an n-type charge storagesub-region is formed particularly beneath an n⁺-type charge storageregion 54 of a sensor unit. The charge storage sub-region is constitutedof three n-type impurity regions including a first charge storagesub-region 61, a second charge storage sub-region 62 and a third chargestorage sub-region 63 as viewed from below.

The charge storage sub-region formed of the first charge storagesub-region 61, second charge storage sub-region 62 and third chargestorage sub-region 63 acts to increase a charge storage capacitance overthe case where the charge storage region 54 alone is deeply formed.

In this way, it becomes possible to make up for the reduction of acharge storage capacitance when pixels are miniaturized and to suppresssensitivity from lowering as will be caused by the miniaturization ofthe pixels.

Additionally, photoelectrons photoelectrically converted at a deepregion of a photodiode can be efficiently transferred.

The first, second and third charge storage sub-regions 61, 62, 63 can besuccessively formed by n-type impurity ion injections of differentenergy levels.

The potential distribution diagram at the section of FIG. 5B is shown inFIG. 6.

As shown in FIG. 6, a potential distribution extended in a direction ofdepth is formed by the formation of the charge storage sub-regions 61,62, 63.

When an n-type impurity is subjected to multistage cycles of ioninjection to form charge storage sub-regions, such a potential along thedepth can be designed.

SUMMARY

As will be seen from FIG. 5A, the charge storage sub-regions 61, 62, 63formed for the aim of improving sensitivity are formed only below thecharge storage region 54, i.e. at the inside of the photodiode.

This is for the aim of suppressing white spots from being worsened andalso suppressing an overflow of stored charges ascribed to the pinningdegradation at the deep portion of the photodiode.

Also in the structure provided with this charge storage sub-region, asthe miniaturization of pixels is advanced, an effective area of thephotodiode is reduced.

At the section of FIG. 5B, the distance between the p⁺ device isolationregions becomes narrower than that at the section of FIG. 5A.

Therefore, in the deep portion of the photodiode, the potential isconstricted owing to an increased effective concentration of the p-typeimpurity caused by the device isolation region 53 and the semiconductorwell region 52. This is illustrated with reference to FIG. 7.

FIG. 7 shows the device isolation region 53 and the semiconductor wellregion 52, which are the p-type impurity regions, after superposing thesectional structure of FIG. 5B over the potential diagram of FIG. 6.

As shown in FIG. 7, an increased effective concentration in the p-typeimpurity regions (i.e. the device isolation region 53 and thesemiconductor well region 52) causes the n-type impurity region to beconstricted with respect to the potential thereof as indicated by thearrows.

This leads to the unlikelihood of a depletion layer being extended tothe depth and sensitivity may take a value lower than a designed one.

As a matter of course, as set out in the Japanese Laid-open PatentApplication No. 2002-164529, when compared with the case where a chargestorage region alone is deeply formed, the provision of the chargestorage sub-regions mitigates the potential constriction along with aneffect of extending the potential toward a direction of depth.

In association with further progress in miniaturization of pixels,however, only the provision of the charge storage sub-regions does notbecome satisfactory.

Accordingly, further ingenuity becomes necessary for securingsensitivity associated with the pixel miniaturization.

In order to solve the above problems, the embodiment of the presenttechnology contemplates to provide a solid-state image pickup device anda method for manufacturing same wherein if pixel miniaturization isfurther advanced, satisfactory sensitivity can be secured, and also to asolid-state image pickup apparatus including the solid-state imagepickup device.

The solid-state image pickup device of the embodiment of the disclosureis one that is constituted of pixels including a sensor unit capable ofphotoelectric conversion therein.

A semiconductor substrate and a charge storage region of a firstconduction type, which is formed in the semiconductor substrate andserves as a sensor unit, are included.

There is further included a charge storage sub-region made of animpurity region of the first conduction type, which is formed, in plurallayers, in the semiconductor substrate beneath the charge storage regionserving as a main charge storage region and wherein at least one or moreof the plural layers is formed entirely across the pixel.

Moreover, a device isolation region that is formed in the semiconductorsubstrate, isolates pixels from one another, and is made of an impurityregion of a second conduction type.

The method for manufacturing a solid-state image pickup device of theembodiment of the disclosure is one wherein pixels are constituted eachincluding a sensor unit capable of photoelectric conversion.

The method includes forming a charge storage sub-region made of animpurity region of a first conduction type entirely of pixels within asemiconductor substrate, and forming plural layers of a charge storagesub-region made of an impurity region of the first conduction type.

Further, the method includes forming a device isolation region isolatingpixels in the semiconductor substrate and made of an impurity region ofa second conduction type and forming a charge storage region of thefirst conduction type serving as a sensor unit on the plural layers ofthe charge storage sub-region in the semiconductor substrate.

The image pickup apparatus of the embodiment of the disclosure includesa focusing optical unit focusing incoming light, a solid-state imagepickup device receiving the incoming light focused by the focusingoptical unit and subjecting to photoelectric conversion, a signalprocessing unit processing a signal obtained by the photoelectricconversion in the solid-state image pickup device.

According to the solid-state image pickup device of the embodiment ofthe disclosure, the plural layers of the charge storage sub-region madeof an impurity region of the first conduction type are formed in thesemiconductor substrate below the charge storage region of the firstconduction type serving as a main charge storage region. When comparedwith the case where a charge storage region alone is deeply formed, thepotential can be extended toward a direction of depth by the provisionof the charge storage sub-region.

Further, because at least one or more of the plural layers of the chargestorage sub-region is formed entirely across a pixel, an effective doseamount of the impurity of the first conduction type at the depth of thesensor unit can be increased. This leads to mitigation of the potentialconstriction from the impurity region of the second conduction typearound the charge storage sub-region and allows a potential distributionin the sensor unit to be spread along a direction of depth and also adepletion layer in the sensor unit to be extended along a direction ofdepth, thereby enabling a saturated charge quantity in the sensor unitto be increased.

According to the method for manufacturing a solid-state image pickupdevice of the embodiment of the disclosure, a charge storage sub-regionmade of an impurity region of a first conduction type is formed entirelyacross pixels in a semiconductor substrate and forming plural layers ofthe charge storage sub-region made of an impurity region of the firstconduction type including the charge storage sub-region formed entirelyacross the pixels. This enables a solid-state image pickup device to bemade as having a structure wherein a depletion layer in a sensor unit tobe extended along a direction of depth thereby ensuring an increasedsaturated charge quantity in the sensor unit.

According to an image pickup apparatus of the embodiment of thedisclosure, the solid-state image pickup apparatus includes such asolid-state image pickup device of this disclosure that a saturatedcharge quantity in the sensor unit can be increased in the image pickupdevice, ensuring satisfactory sensitivity.

According to the embodiment of the disclosure, the solid-state imagepickup device enables a saturated charge quantity in a sensor unit to beincreased, thereby improving the sensitivity of the sensor unit.

Hence, satisfactory sensitivity can be secured if pixel miniaturizationis advanced. Thus, pixels can be miniaturized with the possibility thatthe number of pixels can be increased and down-sizing of a solid-stateimage pickup device can be realized.

According to the embodiment of the disclosure, if the number of pixelsof a solid-state image pickup device is increased or a solid-state imagepickup device is down-sized, there can be realized a solid-state imagepickup apparatus whose sensitivity is satisfactory.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B are, respectively, a schematic configuration view(sectional view) of a solid-state image pickup device according a firstembodiment of the disclosure;

FIG. 2 is a potential distribution diagram of a portion corresponding tothe sectional view of FIG. 1B;

FIGS. 3A to 3E are, respectively, a process chart showing a method ofmanufacturing the solid-state image pickup device of FIGS. 1A and 1B;

FIG. 4 is a schematic configuration view (block diagram) of an imagepickup apparatus according to a second embodiment of the disclosure;

FIGS. 5A and 5B are, respectively, a schematic configuration view(sectional view) of a solid-state image pickup device having a structurewherein charge storage sub-regions are formed beneath a main chargestorage region;

FIG. 6 is a potential distribution diagram of a portion corresponding tothe sectional view of FIG. 5B; and

FIG. 7 is a view illustrating a potential variation in the solid-stateimage pickup device of FIGS. 5A and 5B.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments for carrying out the disclosure are now described.

The description is made in the following order.

-   1. First Embodiment (Solid State Image Pickup Device)-   2. Second Embodiment (Image Pickup Apparatus)    <1. First Embodiment>

The schematic configuration view (sectional view) of a solid-state imagepickup device according to the first embodiment of the disclosure isshown in FIGS. 1A and 1B. FIG. 1A shows a sectional view at a faceintersecting at a right angle with a transfer gate and FIG. 1B shows asectional view taken along line A-A′ of FIG. 1A.

This solid-state image pickup device is configured to form, on a surfaceof an n⁻ semiconductor substrate 1 made of silicon or othersemiconductor, a photodiode (PD) of a sensor unit, a charge transferunit in the form of a transfer gate 7, and a floating diffusion (FD) 6.

As the semiconductor substrate 1, there can be used a semiconductorsubstrate (silicon substrate or the like) or a semiconductor substrateand a semiconductor epitaxial layer formed thereon.

A p-type semiconductor well region 2 is formed as buried in thesemiconductor substrate 1.

This semiconductor well region 2 is formed across an entire surface of apixel region or an entire surface of a chip of the solid-state imagepickup device and isolates the substrate and the pixel unit from eachother. An overflow barrier is formed by means of this semiconductor wellregion 2.

Individual pixels are isolated with p⁺ device isolation regions 3 abovethe semiconductor well region 2. In the inside isolated with the deviceisolation region 3, the photodiode (PD) serving as a sensor unit and thecharge transfer unit are formed.

At the portion of the photodiode, an n⁺ charge storage region 4 isformed, and a p⁺ positive charge storage region 5 for suppressing a darkcurrent is formed on the surface of the charge storage region 4.

At the charge transfer unit, a transfer gate 7 is formed via a thin gateinsulating film, not shown, on the surface of the semiconductorsubstrate 1 and a side wall 8 made of an insulating layer is formed atthe side walls of the transfer gate 7.

The transfer gate 7 may be formed, for example, of polysilicon.

In the surface of the device isolation region 3 provided at the leftside of the figure, an n⁺ floating diffusion (FD) 6 is formed.

The floating diffusion 6 and the positive charge storage region 5 of thesensor unit are, respectively, formed as set in position with thetransfer gate 7 at an outside thereof.

It will be noted that as a variation of the configuration of FIG. 1A,there may be formed the positive charge storage region 5 in positionwith an outer edge of the side wall 8 at the outer side of the transfergate 7.

The transfer gate 7 serves to transfer charges between the photodiodeand the floating diffusion 6. The floating diffusion 6 storestransferred charges.

The charge storage sub-region is formed below the charge storage region4 and includes three n-type impurity regions of a first charge storagesub-region 11, a second charge storage sub-region 12 and a third chargestorage sub-region 12 as viewed from below.

These charge storage sub-regions 11, 12, 13 are formed above the p-typesemiconductor well region 2, i.e. at a depth position between thesemiconductor well region 2 and the charge storage region 4.

The distance between the p⁺ device isolation regions 3 becomes narrowerat the section of FIG. 1B than at the section of FIG. 1A, like thesection shown in FIG. 5B.

Therefore, with the configuration of the section of FIG. 1B, thepotential is constricted at the deep portion of the photodiode owing toan increased effective concentration of the p-type impurities from thedevice isolation region 3 and the semiconductor well region 2.

To avoid this, in this embodiment, the first charge storage sub-region11, which is innermost among the three charge storage sub-regions 11,12, 13, is formed as extended to the device isolation region 3. That is,the first charge storage sub-region 11 is formed entirely across thepixel.

The potential distribution diagram at the section of FIG. 1B is nowshown in FIG. 2.

Since the first charge storage sub-region 11 is widely formedsufficiently to extend to the device isolation region 3, such apotential distribution as shown in FIG. 2 can be formed, which isextended along a direction of depth over the potential distributionshown in FIG. 6.

This is because an effective dose amount of an n-type impurity in thedeep portion of the photodiode can be increased by the wide formation ofthe first charge storage sub-region 11, so that the constriction of thepotential from the surrounding p-type impurity regions 2, 3 can bemitigated.

Since the potential distribution can be widened along a direction ofdepth, the depletion layer within the photodiode can be elongated towarda direction of depth, resulting in improved sensitivity.

More preferably, the first charge storage sub-region 11 formed entirelyacross the pixel is formed at a position of a depth of not smaller than1 μm from the surface of the semiconductor substrate 1.

This enables the depletion layer to be extended at a depth of notsmaller than 1 μm thereby obtaining satisfactory sensitivity to light ina long wavelength region of visible light.

The solid-state image pickup device according to this embodiment can bemade in a manner illustrated hereinbelow.

Initially, as shown in FIG. 3A, a p-type semiconductor well 2 serving asan overflow barrier is formed, by ion injection 21 of a p-type impurity,across the entirety of a semiconductor substrate 1 or the entirety of animage pickup region at a position of a certain depth of thesemiconductor substrate 1.

Next, as shown in FIG. 3B, a first charge storage sub-region 11 isformed by ion injection 22 of an n-type impurity over the semiconductorwell region 2 across the entirety of the semiconductor substrate 1.

Next, as shown in FIG. 3C, using a resist 23 as a mask, a second chargestorage sub-region 12 and a third charge storage sub-region 13 aresuccessively formed on the first charge storage sub-region 11 by ioninjection 24 of an n-type impurity.

It will be noted that the ion injection for forming the first chargestorage sub-region 11, ion injection for forming the second chargestorage sub-region 12 and ion injection for forming the third chargestorage sub-region 13 are carried out at different energies (the orderof energy magnitude is such that first>second>third).

Next, as shown in FIG. 3D, using a resist 25 as a mask, a p⁺ deviceisolation region 3 is formed so as to surround the photodiode of thesensor unit by ion injection 26 of a p-type impurity.

At this stage, an injection amount of the p-type impurity is so selectedas to strike back at the n-type impurity ion-injected entirely acrossthe semiconductor substrate 1. This enables a potential at a boundaryregion between the device isolation region 3 and the photodiode to bedesigned to prevent blooming, color mixing and white spots from beingworsened.

By forming the p⁺ device isolation region 3 in this way, the n-typefirst charge storage sub-region 11 is isolated for every pixel.

Subsequently, as shown in FIG. 3E, a charge storage region 4, a positivecharge storage region 5, a floating diffusion (FD) 6, a transfer gate 7and a side wall 8 are, respectively, formed. These can be formed byhitherto known techniques.

For instance, after the formation of the transfer gate 7, while usingthe transfer gate 7 as a mask, the n⁺ charge storage region 4 is formedby ion injection of an n-type impurity and the p⁺ positive chargestorage region 5 is formed by ion injection of a p-type impurity. Theside wall 8 made of an insulating layer is formed on the side walls ofthe transfer gate 7, and using this side wall 8 as a mask, the floatingdiffusion (FD) 6 is formed by ion injection of an n-type impurity.

Thereafter, a color filter, an on-chip lens and upper wiring layers maybe, respectively, formed, if necessary.

In this way, the solid-state image pickup device shown in FIGS. 1A and1B can be made.

According to the solid-state image pickup device of this embodiment, thefirst charge storage sub-region 11, which is the lowermost layer of thethree n-type charge storage regions 11, 12 and 13, is formed as extendedto the device isolation region 3 and thus, the first charge storagesub-region 11 is formed entirely across the pixel. This enables aneffective dose amount of an n-type impurity at the depth of thephotodiode to be increased and thus, the constriction of the potentialsfrom the surrounding p-type impurity regions 2, 3 can be mitigated towiden a potential distribution toward a direction of depth.

More particularly, the depletion layer in the photodiode can beelongated along a direction of depth and a saturated charge amount canbe increased, thereby improving the sensitivity of the photodiode.

Accordingly, according to the solid-state image pickup device of theembodiment, if a pixel is miniaturized, satisfactory sensitivity isensured. Hence, an increasing number of pixels and down-sizing of asolid-state image pickup device can be realized by the pixelminiaturization.

With above-stated embodiment, only the first charge storage region 11 isformed entirely across the pixel, and the second charge storage region12 and the third charge storage region 13 are formed only at a portionbelow the charge storage region 4.

In this disclosure, where a plurality of charge storage sub-regions areformed below the charge storage region, the number of charge storagesub-regions formed entirely across the pixel is arbitrary.

Accordingly, in case where the three charge storage sub-regions 11, 12,13 as shown in FIGS. 1A and 1B are formed, an arbitrary number of thesub-regions can be formed entirely across the pixel.

More preferably, the charge storage sub-regions formed entirely across apixel are so configured as to be formed over a position where the depththereof from the surface of the semiconductor substrate 1 is at notsmaller than 1 μm.

It will be noted that the charge storage sub-region formed entirelyacross the pixel may be formed by ion injection while using a maskhaving an opening for every pixel instead of the case where they areformed entirely across the semiconductor substrate or image pickupregion like the above-stated manufacturing method.

As in the above-stated manufacturing method, easy formation is ensuredwhen the sub-region is formed entirely across the semiconductorsubstrate or image pickup region and is isolated for every pixel uponformation of a device isolation region.

Although, in the above embodiment, this disclosure is applied to asolid-state image pickup device of a CMOS type wherein the floatingdiffusion (FD) 6 is provided for every pixel, the disclosure may also beapplied to other type of solid-state image pickup device.

For instance, the present disclosure may be applied to a CCD solid-stateimage pickup device as in the afore-mentioned Japanese Laid-open PatentApplication.

In the above embodiment, the charge storage region 4 is formed as ann-type region, with a p⁺ positive charge storage region being formed onits surface.

In this disclosure, contrary to the above embodiment with respect to theconduction type, such a configuration is possible including a p-typecharge storage region and an n⁺ negative charge storage region formedthereon. In this case, plural layers of a p-type impurity region areformed below the charge storage region for use as a charge storagesub-region and at least one or more of the plural layers of the p-typeimpurity region is formed entirely across the pixel.

<2. Second Embodiment>

A schematic configuration view (block diagram) of an image pickupapparatus according to a second embodiment of the disclosure is shown inFIG. 4. This image pickup apparatus includes, for example, videocameras, digital still cameras or cameras for cell phone.

As shown in FIG. 4, an image pickup apparatus 500 has an image pickupunit 501 provided with a solid-state image pickup device (not shown).

A focusing optical system 502 for incoming light gathering and imagefocusing is provided upstream of the image pickup unit 501. At thedownstream of the image pickup unit 501, a signal processor 503 having adrive circuit driving the image pickup unit 501 and a signal processingcircuit processing signals photoelectrically converted into an image inthe solid-state image pickup device are connected. The image signalprocessed in the signal processor 503 can be memorized in an imagememory (not shown).

In such an image pickup apparatus 500, the solid-state image pickupdevice of the disclosure such as the solid-state image pickup device ofthe above-described embodiment can be used as a solid-state image pickupdevice.

According to the image pickup apparatus 500 of the embodiment, there isused the solid-state image pickup device of the disclosure, i.e. asolid-state image pickup device that is configured to ensuresatisfactory sensitivity if miniaturization of pixel is advancing, asdescribed hereinbefore.

This is advantageous in that if the number of pixels of a solid-stateimage pickup device is increased or if a solid-state image pickup deviceis downsized, there can be configured the image pickup apparatus 500wherein satisfactory sensitivity is obtained.

It will be noted that the image pickup apparatus of the disclosure isnot limited to the configuration shown in FIG. 4, but may be applied toimage pickup apparatuses of the types making use of a solid-state imagepickup device.

For instance, a solid-state image pickup device may take a form formedas one chip or may be in the form of a module having an image pickupfunction wherein an image pickup unit and a signal processor or opticalsystem are collectively packaged.

The image pickup apparatus of the disclosure can be applied, forexample, to mobile devices having a camera or image pickup function anda variety of image pickup apparatuses. In a broad meaning, “imagepickup” includes a fingerprint detector and the like.

The present disclosure should not be construed as limited to thoseembodiments stated above, but may take various variations andmodifications without departing from the scope of the disclosure.

The present disclosure contains subject matter related to that disclosedin Japanese Priority Patent Application JP 2010-135612 filed in theJapan Patent Office on Jun. 14, 2010, the entire content of which ishereby incorporated by reference.

It should be understood by those skilled in the art that variousmodifications, combinations, sub-combinations and alterations may occurdepending on design requirements and other factors in so far as they arewithin the scope of the appended claims or the equivalents thereof.

What is claimed is:
 1. A solid-state image pickup device of a typeincluding a plurality of pixels, each pixel is configured to include asensor unit capable of photoelectric conversion, said image pickupdevice comprising: a semiconductor substrate; a charge storage region ofa first conduction type, which is formed in said semiconductor substrateand is configured to be a sensor unit and a main charge storage region;a charge storage sub-region made of an impurity region of the firstconduction type, said charge storage sub-region comprising a pluralityof layers in said semiconductor substrate below said charge storageregion ; and a device isolation region in the semiconductor substrateconfigured to isolate said pixels from one another said device isolationregion made of an impurity region of a second conduction type, wherein,at least one charge storage sub-region layer extends across each pixelto the device isolation region.
 2. The solid-state image pickup deviceaccording to claim 1, wherein, for each pixel, said charge storagesub-region formed entirely across said pixel is formed at a depth of notsmaller than 1 μm from a surface of said semiconductor substrate.
 3. Thesolid-state image pickup device according to claim 1, further comprisinga semiconductor well region, which is formed entirely across each pixelbelow said charge storage sub-region in said semiconductor substrate andis made of an impurity region of the second conduction type.
 4. An imagepickup apparatus comprising: a focusing optical unit focusing incominglight; a solid-state image pickup device comprising a plurality ofpixels, each pixel configured to include a sensor unit capable ofphotoelectric conversion, the solid-state image pickup device furthercomprising (a) a semiconductor substrate, (b) a charge storage region ofa first conduction type in said semiconductor substrate and configuredto be a sensor unit and a main charge storage region, (c) a chargestorage sub-region, made of an impurity region of the first conductiontype, said charge storage sub-region comprising a plurality of layers insaid substrate below said charge storage, and (d) a device isolationregion in said semiconductor substrate configured to isolate said pixelsfrom one another, said device isolation region made of an impurityregion of a second conduction type, wherein, at least one charge storagesub-region layer extends across each pixel to the device isolationregion; and a signal processor processing a signal obtained by thephotoelectric conversion with said solid-state image pickup device.